The intervertebral discs are cartilaginous plates surrounded by a fibrous ring that lie between the vertebral bodies and serve to cushion them. Through degeneration, wear and tear, and trauma, the fibrous tissue (annulus fibrosus) constraining the soft disc material (nucleus pulposus) may tear or become compressed. This squeezing or protrusion of the disc has been called herniated disc, ruptured disc, herniated nucleus pulposus, or prolapsed disc. The extruded nucleus pulposus may press on a spinal nerve, which may result in nerve damage, pain, numbness, muscle weakness and even paralysis.
Common methods of providing relief for damaged intervertebral discs include surgical removal of all or a portion of the intervertebral disc followed by fusion of the adjacent vertebrae. Although fusion can eliminate certain of the aforementioned symptoms, the restricted motion of the fused segment increases the range of motion required of the adjoining intervertebral discs and can therefore enhance their degeneration. As an alternative to fusion, the disc can be replaced with a spacer designed to simulate healthy intervertebral disc motion. The materials from which these disc spacers are made (e.g., polymeric and metallic materials), however, may disintegrate in the body or break down under repeated stress over prolonged periods.
Treating by intradiscal injecting of a material that can dehydrate the nucleus and thereby reduce pressure can be effective if injected in the correct location. However, healthy tissue can be damaged in the event that the injection is not in the correct location. Accordingly, there still exists a need for improved devices and methods for the treatment of intervertebral discs.